You dont actually transfer the memory from C to D.
What you can do is move files, such as pictures, from C to D.
If you have not done this before get someone to show you how, or do it for you, as you could get into a mess.
In future work with and store all pictures on the D drive.
Start treating the D drive as you did the C drive. Save new i tunes and pictures to it.
DONT move any System folders from the C to D. These are the folders used by Windows. Only move files or folders you are CERTAIN are your pictures.
Dont move your music files are this may confuse I tunes.